Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended			6 Months Ended
	Mar. 31, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2012 Internal Revenue Service (IRS) [Member]	Jun. 30, 2012 Colorado [Member]	Jun. 30, 2012 Minnesota [Member]	Jun. 30, 2012 Texas [Member]	Jun. 30, 2012 Wisconsin [Member]
Income Tax Examination [Line Items]
Year(s) no longer subject to audit as statute of limitations has expired				2007
Earliest year subject to examination				2008	2006	2008	2007	2007
Year(s) under examination				None	None	None	None	None
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit - Permanent tax positions		$ 4.4	$ 4.3
Unrecognized tax benefit - Temporary tax positions		28.1	30.4
Unrecognized tax benefit balance		32.5	34.7
NOL and tax credit carryforwards		(31.7)	(33.6)
Amounts accrued for penalties related to unrecognized tax benefits		0	0
Federal Tax Loss Carryback Claims [Abstract]
Tax loss carryback period (in years)	2Y
Discrete tax benefit	$ (15)